It's the seasoning, not the pan itself

Usually the seasoning.

Plain cast iron is just iron. If you could taste the metal, you’d need a lot of it – and your food would probably look gray. The metallic taste almost always comes from the seasoning layer being compromised or not fully cured.

Here’s the deal: A good seasoning is polymerized oil – it’s plastic-like, not oily. If your seasoning is too thin, flaking, or contains rancid oil from improper curing, that’ll give you a weird metallic or bitter taste. Fresh seasoning that hasn’t fully hardened can also do it. The iron itself? You’d need to cook something highly acidic for a long time to leach enough to taste, and even then it’s more “tinny” than “metallic.”

How to tell:

• Look at the pan. If it’s shiny or sticky, your seasoning is undercured or too oily. That’s your culprit.
• If the pan looks dry, patchy, or you see rust spots, you’re tasting exposed iron.
• Try